1. Field of the Invention
Apparatuses consistent with the present invention relate to a light emitting device, a backlight unit using the light emitting device as a light source, and a liquid crystal display (LCD) apparatus adopting the backlight unit, and more particularly, to a light emitting device which emits light asymmetrically, and a direct light type backlight unit that can individually light in units of domains which use a plurality of the light emitting devices as the light source, and an LCD apparatus including the direct light type backlight unit.
2. Description of the Related Art
Liquid crystal display (LCD) apparatuses are light receiving type flat panel display apparatuses that do not generate light by themselves, but instead use external light to display images. A backlight unit is typically installed at the rear of an LCD apparatus to provide a light source for the LCD apparatus.
Cold cathode fluorescence lamps (CCFL) are mainly used as the light source for the backlight unit in LCD apparatuses. However, a CCFL has a relatively short life span, and low color reproducibility. CCFLs have much shorter life spans and lower color reproducibility than light emitting diodes (LED), and have lower instantaneous lighting performances than LEDs.
Therefore, it is difficult to perform lighting with short response times using the CCFL, and thus, it is difficult to use backlight units using CCFLs as the light sources of field sequential LCD apparatuses. A field sequential LCD apparatus requires a backlight unit that can sectionally light in synchronization with screen scanning time. A backlight unit using LEDs as the light source can satisfy the above requirement.
In addition, backlight units can be direct light type backlight units, in which a plurality of light sources installed below the LCD apparatus irradiate the light towards the liquid crystal panel, or edge light type backlight units, in which the light emitted from the light source installed on a side wall of a light guide panel (LGP) is irradiated to the liquid crystal panel, according to the arrangement of light sources.
Direct light type backlight units may use LEDs as point light sources. In backlight units using LEDs as point light sources, the LEDs are arranged in two-dimensional arrays. In particular, the LEDs are arranged to form a plurality of LED lines, and a plurality of LEDs are disposed in each of the lines.
Direct light type backlight units that use LEDs as the light source can be used in field sequential LCD apparatuses.
In field sequential LCD apparatuses using the direct light type backlight unit that uses LEDs as light sources, lighting regions of the LEDs are sectioned into a plurality of domains, and the LEDs light according to a lighting region unit in synchronization with scanning times of the liquid crystal panel. Since red (R), green (G), and blue (B) LEDs are arranged in each of the lighting regions for realizing a color image, the direct light type backlight unit separately operates by the lighting region unit and the color unit to display the RGB colors without using sub-pixels of the liquid crystal panel.
Therefore, the field sequential LCD apparatus does not use a color filter, and thus, original colored light generated by the LEDs can be used without further color modification, and color representation can be improved. However, the above field sequential LCD apparatus has following disadvantages.
In the field sequential method, the LEDs light after the liquid crystal response, and thus, if the R, G, and B color images are displayed sequentially on the screen, when the R image is displayed, the B color of the previous sub-frame is mixed with the R color. For example, when the liquid crystal on a first domain, that is, on the first line, responds before operating the R LED in order to display an R color image, the B light emitted from the B LED that operates on the last domain of the previous sub-frame, that is, the last line of the previous sub-frame, may reach the liquid crystal of the first line. Therefore, some of the B light may be transmitted to the liquid crystal responding in the first domain. When G images and B images are displayed, they are also affected by the above problem.
Therefore, due to the color mixture, color reproducibility of the image as a whole produced by the display apparatus is degraded, and color uniformity is also degraded.